I. Field of the Invention
The present invention relates to wireless communication systems and methods, and in particular to assistive listening systems that facilitate communication in noisy environments.
II. Discussion of Related Art
To facilitate communication in noisy environments, wireless systems may be used to effectively receive and transmit audio signals. In such systems, sounds produced by an audio source are modulated and transmitted wirelessly over, for example, an infrared (IR) or radio signal. At the destination, this signal is intercepted by a receiver that reconstructs the original sounds and plays them back. This method is employed by many commercially-available headphone systems such as the Sony MDR-IF240RK Wireless Headphone System and the Koss HB60 Infrared Clip-On Wireless Headphones.
This method can be used for two-way communication as well. Headsets like the Etymotic Research Link-It and the Comlink Personal Sound Enhancer can produce audio signals using a microphone and wireless transmitter and can also receive signals using a built-in wireless receiver and earpiece speaker.
However, many-to-many communication presents complexities that do not arise in the unidirectional and bidirectional cases described above. An impediment to the development of a system for multi-way signal transmission is the problem of co-channel interference. Traditional signal transmission using amplitude, frequency, or phase modulation of radio-frequency carriers is designed to work with one carrier signal at a time. Mixing multiple carriers in a demodulator can result in badly distorted output.